Compared to conventional locks, electromagnetic locks are, in general, easy to install, quick to operate and sturdy. Due to the capability of fully electronic operation, electromagnetic locks are almost always part of a complete electronic access control system. One potential issue arising from the operation of electromagnetic locks is that they require continuous power to remain locked. Although their power consumption may be typically less than that of conventional light bulbs, the power loss can be significant in the longer term, particularly if there is a need to keep the door in a locked state. Maintaining an electromagnetic lock in the locked state using full power can be especially inefficient in cases where no one really tries to enter or exit the door most of the time.
Conventional electromagnetic locks consist of magnetic wire wrapped around a bobbin which is placed within magnetic laminations. Once electric power is applied, a magnetic force is generated that provides a set holding force and consumes full power at all times. This constant use of full power means that energy is wasted, which goes against the trend of employing energy-saving, or “green,” devices and methods.
A more energy-efficient electromagnetic lock is required that incorporates low-cost sensing techniques to detect a force initiated to open the door. Equipped with such a sensing capability, electromagnetic locks may be operated so that the full power is applied only when an attempt is made to gain entry through the door. The magnetic locks may thus be operated with a very low effective holding strength, drawing very little current, when no force is being applied to open the door, thereby enhancing significantly the energy-efficiency and related operational costs of these devices.